A processor is the portion of a computing system that carries out instructions to implement basic tasks and operations on the system. A central processing unit (CPU) is a type of processor that acts as the main processor for a computer system. A multi-core processor is a single component that includes multiple constituent processors, which are referred to as “cores”.
Regardless of the actual type of processor that is used, the processor operates and performs tasks by reading and executing program instructions. Instruction scheduling is the process of managing resource allocation to execute instructions. An instruction scheduler is the component in a processor (or core within a processor) that manages the order and flow in which instructions are provided to execution units.
Many processors also implement multi-threaded processing, in which multiple threads of execution can operate in parallel to perform work in the processing system. The multiple threads in a multi-threaded system will share the resources of a single processor (e.g., including one or more cores) to perform their processing. Since the multiple threads are sharing the same basic resources, this means that there is likely to be contention for the resources that are needed to process the instructions issued by each thread.
In a multi-threaded system, instructions can therefore be scheduled with consideration of allocation of execution resources among the different threads. Thread-based scheduling is performed to make sure that the threads are allocated an appropriate amount of system resources to perform their processing.
There are many possible schemes that can be used to implement scheduling for a multi-threaded system. For example, a very straightforward approach to implement scheduling is to provide a round-robin allocation of execution resources to each thread, where instructions for the threads are selected in a round-robin order for execution. Another possible scheduling scheme is give the highest priority to the thread that currently has the lightest current execution workload (i.e., giving the highest priority to the thread having the lowest number of instructions currently being processed in the instruction pipeline).
The problem with these approaches is that they are all quite simplistic and may be disadvantageous in complicated processing scenarios when greater control is needed over the scheduling. Another issue with these approaches is that they contain relatively static allocation algorithms that do not allow for flexibility in how the scheduling is performed, which could create performance problems in the event of changing conditions where there may otherwise be a desire to change allocation of resources to the different threads.
Therefore, there is a need for an improved approach to efficiently and effectively perform scheduling in a multi-threaded system.